Question

下面的Python程序启动一个线程，然后继续在主线程中执行操作。我将整个主线程包装在try-except块中，这样如果发生异常，我可以拆除所有正在运行的线程。

当我使用Python 2.7.5运行脚本并在程序执行期间随机调用KeyboardInterrupt时，会触发异常但不会捕获异常。该计划继续运行。

$ python test.py 
Running server ...
Searching for servers ...
^CTraceback (most recent call last):
  File "test.py", line 50, in <module>
    main()
  File "test.py", line 40, in main
    app_main()
  File "test.py", line 35, in app_main
    searchservers()
  File "test.py", line 26, in searchservers
    time.sleep(0.0005)
KeyboardInterrupt

我错过输出中的一行，当发生异常时，该行会在main()中打印。

代码

import time
import threading

thread_pool = []
running = False

def stop():
    global running
    running = False

def runserver():
    print "Running server ..."

    global running
    running = True

    while running:
        time.sleep(0.07)

def searchservers():
    print "Searching for servers ..."

    for i in xrange(256):
        for j in xrange(256):
            time.sleep(0.0005)

def app_main():
    server = threading.Thread(target=runserver)
    thread_pool.append(server)
    server.start()

    time.sleep(0.1)

    searchservers()
    stop()

def main():
    try:
        app_main()
    except Exception as exc:
        stop()
        print "%s occured, joining all threads..." % exc.__class__.__name__
        for thread in thread_pool:
            thread.join()

        raise exc

if __name__ == "__main__":
    main()

为什么没有锁定KeyboardInterrupt？在线程程序中捕获异常并拆除整个过程的正确方法是什么？

Answer 1

KeyboardInterrupt是特殊例外;与MemoryError，GeneratorExit和SystemExit一样，它来自基类Exception类。

仅仅抓住Exception是不够的;你通常会明确地抓住它：

except (Exception, KeyboardInterrupt) as exc:

但是，您也在尝试捕获线程中的异常;线程有自己独立的堆栈;你不能只是去捕捉主线程中那些堆栈中抛出的异常。您必须在该线程中捕获异常：

def runserver(): print "Running server ..." global running running = True try: while running: time.sleep(0.07) except (Exception, KeyboardInterrupt) as exc: print "Error in the runserver thread"

要以通用方式处理此问题并将“异常”传递给主线程，您需要某种线程间通信。请参阅Catch a thread's exception in the caller thread in Python以获得完整的解决方案。

无法在线程程序中捕获异常

代码

1 个答案: